**What is ISO/CIE 11664-3- CIE tristimulus values about?**

ISO/CIE 11664 is a safety standard on colorimetry.

ISO/CIE 11664-3 is the third part of the ISO/CIE 11664 series of documents that specifies methods of calculating the tristimulus values of color stimuli for which the spectral distributions are provided. These color stimuli can be produced by self-luminous light sources or by reflecting or transmitting objects.

ISO/CIE 11664-3 requires that the color stimulus function be tabulated at measurement intervals of 5 nm or less in a wavelength range of at least 380 nm to 780 nm. Extrapolation methods are suggested for cases where the measured wavelength range is less than 380 nm to 780 nm.

Note 1: ISO/CIE 11664-3 is defined as summation at 1 nm intervals over the wavelength range from 360 nm to 830 nm. Alternative abridged methods are defined for larger intervals (up to 5 nm) and shorter ranges (down to 380 nm to 780 nm). The alternative methods are to be used only when appropriate and when the user has reviewed the impact on the final results.

Note 2: ISO/CIE 11664-3 is used in conjunction with the CIE 1931 standard colorimetric observer or the CIE 1964 standard colorimetric observer.

**Who is ISO/CIE 11664-3- CIE tristimulus values for?**

ISO/CIE 11664-3 on CIE tristimulus values is relevant to:

Manufacturers of colorimeter
Textile industries
Food industries
Manufacturers of paint
Manufacturers of color spectrometer

**Why should you use ISO/CIE 11664-3- CIE tristimulus values?**

Colors with different spectral compositions can look alike.

An important function of colorimetry is to determine which stimuli look alike to a given observer with a given set of color matching functions. This is done by calculating a set of three tristimulus values for each stimulus. Equality of tristimulus values indicates equality of color appearance under equal irradiation and viewing conditions.

ISO/CIE 11664-3 is based on long-standing CIE recommendations for the calculation of tristimulus values. ISO/CIE 11664-3 is used in conjunction with the CIE 1931 standard colorimetric observer or the CIE 1964 standard colorimetric observer. If the angle subtended at the eye by the color stimulus (or fields to be matched in color) is between about 1° and 4° the CIE 1931 standard colorimetric observer shall be used. If this angular subtense is greater than 4° the CIE 1964 standard colorimetric observer shall be used. The same colorimetric observer shall be used for all stimuli to be compared with each other. Tristimulus values are often evaluated on a relative basis. In such cases, the relative color stimulus function, φ(λ), may be used instead of the color stimulus function, φλ(λ). It is essential that, for stimuli that will be considered together, all the spectral distributions involved be assessed on the same relative basis.

Overall, ISO/CIE 11664-3 is useful as it provides assistance on a colorimeter that involves the measurement of color and is used for finding the concentration.

What’s changed since the last update?

BS EN ISO/CIE 11664-3:2019 supersedes EN ISO 11664-3:2013.

BS EN ISO/CIE 11664-3:2019 replaces ISO 11664-3:2012 | CIE S 014-3:2011, of which it constitutes a minor revision, incorporating minor editorial updates.

BS EN ISO/CIE 11664-3:2019

Colorimetry - CIE tristimulus values

Current

Published:

31 Jul 2019